(a) Field of the Invention
The present invention relates generally to a two-dimensional light source using light emitting diodes (LEDs), and more particularly to a surface light source used in backlighting a liquid crystal display (LCD) device and an LCD device using the same.
(b) Description of the Related Art
Display devices used to display images, such as television receivers and computer monitors, are classified into self-luminescence display devices capable of self-emitting and light receiving display devices requiring a separate light source. Light emitting diodes (LEDs), electroluminescence (EL) devices, vacuum fluorescent display (VFD) devices, field emission display (FED) devices, plasma display panel (PDP) devices, etc., are included among self-luminescence display devices, while liquid crystal display (LCD) devices, etc., are included among light receiving display devices.
Generally, an LCD device includes two panels that each have field generating electrodes on their inner surfaces, and a dielectric anisotropy liquid crystal layer interposed between the two panels. In the LCD device, a variation of a voltage difference between the field generating electrodes, i.e., a variation in strength of an electric field generated by the field generating electrodes, changes the transmittance of light passing through the LCD device, and thus images are obtained by controlling the voltage difference between the field generating electrodes. In the LCD device, light may be either natural light or artificial light emitted by a light source separately employed in the LCD device.
A backlight is a representative device for providing artificial light to the LCD device and utilizes light emitting diodes (LEDs) or fluorescent lamps, such as cold cathode fluorescent lamps (CCFLs), external electrode fluorescent lamps (EEFLs), etc., as the light source.
LEDs have eco-friendly characteristics since they do not use mercury (Hg), and a working lifetime of the LEDs is longer than working lifetimes of most other light sources due to stable characteristics of the LEDs. For these reasons, LEDs are especially popular for use as next-generation light sources.
However, light emitted from the LEDs tends to be condensed to a substantially narrow area. Accordingly, for applying the LEDs to a surface light source (two-dimensional light source), various optical films capable of distributing light to a wider region are required. Additionally, a space for allowing light dispersion within the LCD device is required. An assembly process of such optical films makes a fabrication process of the LCD device more complex and the space required for allowing light dispersion may impede fabrication of a thinner device.